Because they were abject morons who refused to inform themselves.
Shouldn't Trump The Great and Powerful have possessed a mininum of sagelike wisdom that would have allowed him to read and listen, and understand what Obama was/is? We all did.
I guess that just makes him another moron. Or a Democrat.
Same thing, really.
We could ask the same question from some other candidates who supported and voted for TPP/TPA, can’t we?